1. Field
One embodiment of the invention relates to shading correction of the ambient light quantity of a lens, generated in an imaging apparatus using an imaging element such as a triple-CCD imaging sensor and a triple-CMOS imaging sensor.
2. Description of the Related Art
In an imaging apparatus for imaging an object by means of a lens, it has been known that light quantity around a lens is decreased with respect to image light entering at the center of a lens.
Thus, in an imaging apparatus, light quantity decreased in a marginal area is usually corrected as shading correction of ambient light quantity.
Japanese Patent Application Publication (KOKAI) No. 2005-277618 discloses shading correction, in which a function of sum of a square of horizontal distance and vertical distance from the center of an image to each pixel is obtained by calculation, and is corrected for each color.
Japanese Patent Application Publication (KOKAI) No. 2004-165958 discloses correction of limb darkening by computing a function of sum of a square of horizontal distance X and vertical distance Y from the center of an image to each pixel.
Japanese Patent Application Publication (KOKAI) No. 2003-101844 discloses display of an image by rotating along the directions (vertical and horizontal directions) of a camera.
Japanese Patent Application Publication (KOKAI) No. Hei-11 150681 discloses an apparatus, in which electronic correction of a decrease in ambient light quantity, i.e. correction of light quantity is omitted in a certain range from the center of an image.
Japanese Patent Application Publication (KOKAI) No. Hei-11 164194 discloses an image processing method using quadratic, tertiary, or quartic equation according to the height of an image for compensating limb darkening.
Neither of the above patent applications, No. 2005-277618 and No. 2004-165958, mentions correction of a decrease in a signal level different for R, G and B, by using a triple-CCD imaging apparatus. Neither application describes color shading (coloring) in a marginal area of a screen, as a decrease in a signal level is different for each color component.
Both of the correction methods disclosed in the above patent applications, No. 2005-277618 and No. 2004-165958, needs large memory capacity for storing image data.
It is difficult for any one of the methods and apparatus disclosed in the above patent applications, No. 2003-101844, No. Hei-11 150681 and No. Hei-11 164194 to decrease color shading caused by the influence of a decrease in ambient light quantity occurred when three CCDs or CMOS sensors are used.